The replacement of utility lines is a significant part of the renewing of the infrastructure within the United States and other countries of the world. More and more this replacement work is done without digging trenches to remove the old pipes and installing the new pipes. Also the trend is to use polyethylene pipe as the replacement pipe. The present invention is directed to a unique pulling attachment for plastic, usually polyethylene, pipe and a slip lining head to pull the polyethylene pipe through the old pipe.
Slip lining of sewer lines with a polyethylene pipe has been an industry standard for some time. However, the approach has been essentially one of brute force. There are two significant problems with the approach taken to date with slip lining. The first is the manner in which the polyethylene pipe is attached to the slip lining head. The most common approach to the attachment of the polyethylene pipe to the head is with a set of collars which encircle the outside of the polyethylene pipe and are attached to the head with a series of bolts. The problem encountered in the field is the combined weight and bulk of the pipe and head in attempting to attach the two together. The pipe must be lifted and placed over the connecting sleeve of the head which has a plurality of threaded holes which must be aligned with the holes in the collars. A power drill is required to cut holes in the polyethylene pipe for the bolts to pass through the openings in the collars and be threaded into the holes of the sleeve of the head. What appears to be an easy operation, is a difficult operation when done in the field. In the field neither the pipe, which may be forty feet long or fused to a length of several hundred feet, nor the head can be rotated to make the connection but the person making the connection must move around and under the pipe to make the openings in the end of the plastic pipe for the bolts. The importance of the attachment can not be over emphasized since if the pipe pulls away from the head then the operation comes to a costly stop. The present invention overcomes the problems with the attachments now being used.
The second problem with slip lining heads presently used is that they were designed with brute force as the only criteria. In most instances the presently used heads are large and long. The shape of the pulling or front end of the presently used head is generally tapered with a long inclined plane. No apparent thought or consideration was given to the potential problems which might be encountered and providing any design solution to those problems in the construction of the slip lining heads which are presently used.